A TDS meter is a small hand-held device used to indicate the Total Dissolved Solids in a solution, usually water. Since dissolved ionized solids, such as salts and minerals, increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that reading. Many TDS meters display the TDS in parts per million (ppm); 1 ppm indicates 1 milligram of dissolved solids per kilogram of water.







First, it’s important to know what TDS really is: Total Dissolved Solids. After water falls to the ground as rain, it dissolves the minerals present in the rocks and soil it passes over or through. As it dissolves these minerals, they remain in the water at varying levels of concentration. This is a very natural process and it helps make water taste “right” by slightly raising the pH of the water. The most common minerals found in water are Calcium, Magnesium, and Sodium.

Some areas of the country have higher levels of these dissolved minerals in their water making it “hard” and other areas have lower levels. Anything under 200 mg/L (or ppm) is good and 100 mg/L is considered excellent. As the TDS level goes below this level (as the minerals are removed) the water has a lower pH and becomes more acidic or corrosive. This causes a noticeable difference in the taste of the water. TDS levels over 400 mg/L are considered non-potable (don’t drink that stuff).

Knowing your TDS level is important when considering a Salt-free Water Conditioner for your home. Salt-free Water Conditioners can protect pipes and plumbing, decrease spots and stains on dishes and shower doors, increase the life of brighter clothing, and more, without wasting salt or water. Keep in mind a water filter is not a water conditioner. The ultimate goal of a water filter is not to remove all solids in the water.



A TDS meter does not measure contaminants. It will not tell you if your water is healthy. Some healthy minerals like potassium, magnesium, and calcium can actually cause your TDS meter to spike.  So, any water filter with a remineralizer will cause the opposite effect on a TDS meter than you expect. Your water could also have heavy metals like lead, or other contaminants like pesticides, pharmaceuticals, or hexavalent chromium. The TDS meter will not pick these contaminants up.